/*
 * Copyright (C) 2016 Apple Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include "Condition.h"
#include "Deque.h"
#include "HashSet.h"
#include "Lock.h"
#include "Locker.h"

namespace WTF {

    template<typename T, size_t BufferSize>
    class SynchronizedFixedQueue {
    public:
        SynchronizedFixedQueue() {
            static_assert(!((BufferSize - 1) & BufferSize), "BufferSize must be power of 2.");
        }

        void open() {
            LockHolder lockHolder(m_mutex);
            if (m_open)
                return;

            // Restore the queue to its original state.
            m_open = true;
            m_queue.clear();
        }

        void close() {
            LockHolder lockHolder(m_mutex);
            if (!m_open)
                return;

            // Wake all the sleeping threads up with a closing state.
            m_open = false;
            m_condition.notifyAll();
        }

        bool isOpen() {
            LockHolder lockHolder(m_mutex);
            return m_open;
        }

        bool enqueue(const T &value) {
            LockHolder lockHolder(m_mutex);

            // Wait for an empty place to be available in the queue.
            m_condition.wait(m_mutex, [this]() { return !m_open || m_queue.size() < BufferSize; });

            // The queue is closing, exit immediately.
            if (!m_open)
                return false;

            // Add the item in the queue.
            m_queue.append(value);

            // Notify the other threads that an item was added to the queue.
            m_condition.notifyAll();
            return true;
        }

        bool dequeue(T &value) {
            LockHolder lockHolder(m_mutex);

            // Wait for an item to be added.
            m_condition.wait(m_mutex, [this]() { return !m_open || m_queue.size(); });

            // The queue is closing, exit immediately.
            if (!m_open)
                return false;

            // Get a copy from m_queue.first and then remove it.
            value = m_queue.first();
            m_queue.removeFirst();

            // Notify the other threads that an item was removed from the queue.
            m_condition.notifyAll();
            return true;
        }

    private:
        Lock m_mutex;
        Condition m_condition;

        bool m_open{true};
        Deque<T, BufferSize> m_queue;
    };

}

using WTF::SynchronizedFixedQueue;
